Hi,

a brief outline of the config steps:

aaa new-model

create 2 separate radius servers, use the modern syntax with host and key in the same line

radius-server host 10.1.1.1 key XXXXXXXXX

radius-server host 10.1.1.2 key XXXXXXXXX

create 2 separate aaa group-servers radgroup1 and radgroup2 and add each of the servers to one aaa group server

aaa group server radius radgroup1 

 server 10.1.1.1
aaa group server radius radgroup2
 server 10.1.1.2

create 2 aaa authentication lists with different group servers as a method:

aaa authenticate ppp login1 group radgroup1

aaa authenticate ppp login2 group radgroup2

use the two authetications on the apropriate interfaces:

router(config)#interface {name-of-interface-1}

router(config-if)#ppp authenticate chap login1

router(config)#interface {name-of-interface-2}

router(config-if)#ppp authenticate chap login2

rgds,

MiKa